Two employees at Sharm el Sheikh International Airport have been arrested by Egyptian authorities over the bombing of Metrojet Flight 9268, which Russia has confirmed was caused by an “act of terrorism”.

Egyptian security officials say 17 people have been detained following the 31 October attack, which killed 224 people.

Only two are suspected of providing direct assistance to those who planted a bomb aboard the Russian airliner, which crashed in the Sinai Peninsula.

The arrests come after the Federal Security Service (FSB) confirmed it was treating the crash as a terror strike targeting Russian nationals.

US and British intelligence has long suggested the crash was caused by an act of terror, with a member of an investigation team saying they were “90% sure” that a noise heard on the black box was a bomb .

Russia has offered a $50m (£33m) reward for information which leads to the arrest of those responsible.

Alexander Bortnikov, the head of the FSB, spoke to President Vladimir Putin to reveal details of the Russian investigation into the crash.

“We have carried out investigations of the plane fragments and the luggage. We could find traces of a foreign-made explosive device, an improvised explosive device,” he said.

“(An) equivalent of up to one 1.5kg of TNT went off during the flight. As a result the plane disintegrated in mid-air, which explains widely scattered fuselage pieces.

“I can therefore unequivocally say that this was an act of terrorism.”

Mr Putin described the downing of the plane as a “barbarian” terror attack and “one of the bloodiest crimes” perpetrated on Russian citizens.

“The killing of our people in the Sinai Peninsula is one of the bloodiest crimes,” he said.

“We are not going to wipe tears from our souls and our hearts. This will remain with us forever.

“But this will not prevent us from finding and punishing the criminals. We should be looking for them, no matter how much time passes.

“We need to know them by their names. We will find them, wherever they are, and we will punish them.”

The Metrojet airliner crashed shortly after taking off from Egypt‘s Sharm el Sheikh International Airport. All 224 people aboard the Airbus A321 died.

Thousands of Britons were stuck in the popular holiday resort in the wake of the attack as the UK and several other countries suspended flights over security concerns.